I'm building a slant six for my '75 Scamp (daily driver) as well as converting to a 4 speed overdrive transmission.

Slant six is basically stock, bored .40 over, super six setup.

I'm planning on installing dual exhaust via split manifold out the back.

What pipe diam. would ya'll recommend? Also, what type of mufflers?

I tried searching and didn't seem to find anything.

Thanks

There has been plenty of discussion on exhaust. Single and dual. If you really want the added weight and expense of duals it's up to you.

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Joshua

Okay, Thanks for the input, but that didn't answer my question. I already know i'm putting on the dual pipes..what I asked was:

What size pipe?

Thanks again.

You can run fairly small diameter pipe once you get to the mufflers.

For duals, from your collectors, go 1-7/8" or 2" max to the mufflers. From the mufflers back, decrease the size again to keep velocity up as the gasses cool. In this case smaller is better for a couple reasons.

1. Smaller diameter pipe is lighter. No sense adding a bunch of weight.

2. Keeping the velocity of the exhaust gas up helps with scavenging, and the exhaust system will dry more quickly.

For performance reasons, the better route for a street or street/strip car would be to bring them into a dual inlet muffler, then bring a single tail pipe out. A system like this will dry out more quickly, and therefore live longer.

Since your set on duals, go down to 1-1/2" or at maximum 1-7/8" over the axles.

Going bigger can sound different, so that may be the route you choose to take. It will rot out more quickly, and performance will suffer on a mild engine.

For mufflers, that's up to your preference. It depends on the sound you want, and budget.
I run a single Xlerator muffler, but I run a 2-1/4" Single off Dual Dutra Duals, a Carter 500 AFB, 10.7:1, 250 CI Stroker. Duals would just weigh me down. Having it to do over again, I'd decrease the head pipe size off the duals, run 2-1/4" to the muffler, and 1-7/8" over the axle.

Josh knows what he's about. He builds some awesome slant cars, and he's right on this one. Not what you wanted to hear, but a single will perform better in this case. Without a seriously radical build, there is no performance advantage with true dual exhaust.

CJ

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Part of Tyrde-Browne Racing

Ceej:

Ceej,

I can’t find a local vender here in Maine that carries these interesting AP Products. Do you know of one on line that ships?

Also can you make a sound recording of the sound that your car produces equipped with the Xlerator at idle, & mid 2000 rpm drone-zone?

I have had it with the noise & drone from my machine. As you know, none of the muffler sound recordings found on muffler websites employ beefed up straight sixes. The sound from these engines can be made soft & enjoyable to loud, droning, and head splitting.

Subject for a sticky:

A library of different muffler & exhaust pipe configurations, and the sound they produce. What is music to one man’s ear is pure hell to another’s.

I believe this would be helpful to those of us not wanting to spend a bunch of bucks & time experimenting with different combinations. I know it has prevented my self from changing my exhaust system from the devil I know to the devil I don’t know.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

I'm not sure you will be able to hear the exhaust over the Holley Red pump transmitting through the aluminum trunk fire wall!

I'll try when we get home from Woodburn. Perhaps somebody can do a video of the car today, and you'll get an idea what it sounds like.

CJ

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Part of Tyrde-Browne Racing

Another person that's too lazy to use the search function and wants instant gratitfication. Like he said, there's been tons of discussion.

Thank you Ceej. I appreciate you taking the time to give me some real information to help me in my project.
I searched for topics and found no information on pipe size for true dual exhaust, I found "tons of discussion" on single pipe size. Some of you guys really know how to treat people. Why don't you get off your high pedestal for a change?

Thanks again!

I'm torn between being helpful and pointing out the lovely mixed metaphor. Hey lets do both! I'm not on a high horse or a pedestal so here goes...

One way to answer your own question is to search off this board and find typical exhaust sizes for the amount of horsepower developed. Or you could take the cross sectional area of the inside of a single 2.25-2.5" pipe, divide by two and find the closest cross sectional area of the pipe to be used for duals. By cross sectional area two 1 7/8" pipes are larger than a single 2.5" pipe, but there is more internal surface area and greater boundary layer effect which will constrict flow somewhat. 1 3/4" tube is easier to find and the internal area of two 1 3/4" tubes falls between that of a single 2.25" and 2.5" tube.

30' of 1.75" aluminized 16 gauge exhaust tubing weighs 35.1 lbs.
15' of 2.5" aluminized 16 gauge exhaust tubing weighs 25.35 lbs.

This is interesting... A 17771 Dynomax Super Turbo muffler with a 3 1/4" x 7 3/4" case, 18 1/2" long and 1.75" connections is about $63 and you need two. A Dynomax 17733 with the larger 4 1/4" x 9 3/4" case also 18" long and 2.5" connections is about $47 and you only need one. The 25 1/2" long case 2.5" Dynomax 17748 is about $53. So even if you used the longer case 2.5" muffler you save $73 which easily pays for a pre-fab Y-pipe. I wonder about the weight difference between two 17771s and a single 17748.

I'm also curious to know what the exhaust shop will charger to bend and hang two full length pipes and mufflers as opposed to two pipes from the manifolds to a Y at the transmission crossmember, a single pipe to the muffler and a single tail pipe.

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Joshua

Ceej:
[quote]I'll try when we get home from Woodburn. Perhaps somebody can do a video of the car today, and you'll get an idea what it sounds like. [/quote]

That would be nice, thanks CJ

A side story below:

I'm riddled with ADD this afternoon, and should be raking out rocks to finish planting my new lawn, but I'm just too lazy and the air is dry, and parts for the Dart are still in transit, ants keep crawling on top of my desk while sitting here, note to self find the 20 year old ant killer that is still packed somewhere, and I am having the greatest urge to graze out of the frig every fifteen minutes...

Ok, the exhausting story, with practically no point. You read it, while I hit the frig one more time.

To be honest, I don’t quite know what sound I’m looking for coming out the back of the Dart; [url=http://www.imcdb.org/vehicle_1820-Aston-Martin-DB5-1964.html] DB4[/url], [url=http://www.flickr.com/photos/autohistorian/4390122691/] Mark IV [/url]or 140 Jaguar, late model BMW, or what, but when I hear it, I’ll know.

Years ago, a friend had a [url=http://en.wikipedia.org/wiki/Bentley_Mark_VI1949] Mark VI Bentley[/url], that sounded good but barely auditable, the muffler was about 4.5 feet long & 10 inch in diameter, which works real good when your wheel base is 120 inches, and a foot off the ground.

About that same time, early 70's, while attending a car show, I ran across a fellow that had the same model which car he used in his real estate biz. We had a bit of muffler chatter, and found out he to had need to repair his exhaust system. I remember this well; he was real proud of his inexpensive answer to the ungodly expensive RR giant sized “silencerâ€￾ fitted to those Bentley’s: a 1952 Chevy exhaust system… You must remember that set-up; the one with the flattened down tail pipe.

One guess what the fine English saloon car sounded like inside & out? You guessed it; the cheapest thing General Motors made in ’52. Yuck. Even had that same annoying start-up buzz those post war Chevy six banger’s have. A whole stick of red lipstick wouldn’t have dressed that bad girl up equipped with that plumbing job…

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Now thats some useful information! haha

I've read the pros and cons of single vs. dual pipes on here...I just like the way the duals sound...and since I'm really not looking for some kind of performance machine, i'm fine with possibly sacrificing some performance plus the added weight. She's just my driver so why not?

Mufflers however, thats another story. I usually just run some cheap turbo mufflers on my cars. On a V8 they sound pretty good, but i'm not sure about a six. I also don't want an annoying loud drone inside when I'm cruising down the street. Half the time I can't tell if the car is running unless I check the oil light to see if it is off. I do still have the cat on the car though, so i'm not sure if that has much of any effect.

That's cool. Try to limit the size of the tail pipe for the above mentioned reasons. It will change the tone of your exhaust by going smaller. I agree. I like the sounds of duals, and the bigger, the better they sound to me. You have to remember that a bunch of us are racing fanatics, and function over-rides form for many of us!

Duster idiot has a wicked sounding set of duals on his Hyperpak Feather Duster. He daily drives it, so perhaps he can lend a hand with his pipe size. He's running Dutra Duals. The 600 Holley likely adds to the resonance too!

Fopar runs duals on his 53 Ford off headers. That car spends a lot of time making town runs, and when you still could get him out of his bunny slippers before noon, he drove it to work every day. He can likely add some ideas for you. He runs a 600 Carter that feeds from a dual snorkel cold air intake.



CJ

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Part of Tyrde-Browne Racing

I would also vote for duals - a lot of older guys I know (who modded slant sixes back in the day) always tell me a split manifold and dual exhaust will sound awesome on my slant.

I decided to go with a set of Cragars instead right now - body in process of being reborn right now.

I am running 2" duals off of Clifford headers to an H to chambered mufflers terminating before the rear axle. IT'S EFFING LOUD!! But it sounds awesome at idle, the drone may drive me insane before long though. May need a dif choice in mufflers?!

,Cliff

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'72 4 dr Dart
'63 4 dr Dart

Ceej, I still have that g-tech video on YouTube.

~RDE~

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1984 D100 Shorty Custom
Certified Auto Appraiser - RevItUp Classic Appraisals
President - Cherry City Bombers CC
Part of Tyrde-Browne Racing